Following the integration guide on handling IPN notifications:
https://amazonpaycheckoutintegrationguide.s3.amazonaws.com/amazon-pay-checkout/set-up-instant-payment-notifications.html#ipn-types
Chargeback notification can be initiated, but the only way to handle it is:
Look up chargeback details in Seller Central using the chargePermissionId
This is inconsistent with v1 API, where chargeback information was normally included in IPN.
Therefore I believe that chargeback object get method is clearly missing in v2 API.